The present invention relates to an image processing apparatus which receives input image data in the form of separated data, combines those data, and outputs the combined one. Further, the present invention also relates to an image processing method. Besides, the present invention may be also applied to color facsimile machines, or to transmission/reception of images on the Internet.
The facsimile communication through public lines and the image or visual communication through the networks of public lines and LANs are widely used at present. Various types of machines for transmitting and receiving image data are presented, for example, facsimile machines, personal computers, multi-function digital copying machines, and network printers. The market and technical progress have rapidly replaced those old machines handling only monochromatic or black/white images with the machines capable of handling color images. In particular color facsimile machines and color printers takes a major market share. The network system may interconnect different types of machines of different resolutions or different color spaces, e.g., color copying machines and monochrome copying machines.
In the image data communication between the machines of different image structures, an original image input to the machine is usually handled as one plane image. The sender side judges the type of original document, selects the process most appropriate to the judged original, applies the appropriate process to the plane image over its entire image, and sends the processed image data to the receiver side. If an original image, i.e., an image on an original document, is represented by image data of one attribute, viz., it consists of only characters or photograph, no problem arises in handling the original image as a single plane image. However, problem arises if the original image has two or larger number of attributes, for example, the original image contains characters and photograph. To compress the image data containing character or textual data and pictorial data, the same data compression method is applied to both the textual and pictorial image data. In this case, in some type of data compression method, a data compression ratio of the textual image data is different from that of the pictorial image data, and this results in deterioration of the image quality of the textual or pictorial image data.
The resolution, the color space, and the number of gradation levels of the image data, which define the image structure of the image data, are sometimes converted before the transmission of the image data in order to reduce the amount of data to be transmitted. Also in this case, the image data is entirely processed by the same image-structure conversion process. Where it is required that a part of the image data is transmitted in high image quality, it is necessary to transmit the whole image data in high image quality. This results in increase of the amount of the image data transmitted. Where it is required that the image data is transmitted in a real time fashion or at high speed, the image data must be transmitted at low resolution. In this case, the image quality is inevitably deteriorated.
A target image structure to which the image structure of the input image data is converted is determined in the sender side. In the network image communication, the target image structure determined in the sender side is not always coincident with the image structure in the receiver side. For example, the resolution of the input device in the sender side is sometimes different from that of the output device in the receiver side. Other factors defining the image structure, such as the color space, the number of gradation levels, and the screen structure, are also different between the sender side and the receiver side frequently. To transmit the image data whose image structure is different from that in the receiver side, the image structure of the image data in the sender side must be conformed to that of the output device.
Accordingly, an object of the present invention is to provide an image processing apparatus which provides a high speed transmission of image data, exactly reproduces an original image of high quality, and outputs the image data whose image structure is conformed to the image structure of the output device.
Another object of the present invention is to provide an image-structure converting method which allows the image processing apparatus having the above useful functions to operate.
In the present invention, input image data is received in the form of at least three separated data, a first piece of image data, a second piece of image data, and selection data to selectively specify the first piece or the second piece of image data, and the first piece and the second piece of image data are combined and then output. The first piece and the second piece of image data, and the selection data are subjected to the image-structure conversion process, e.g., resolution conversion process and color-space conversion process, and the compression process, which are selected in consideration with their data characteristics and the best for those separated data. For the data not requiring high resolution, its resolution is converted into a low resolution. For the data requiring high resolution, the data is processed while at high resolution. Thus, the separated data having different image structures are received, and an original image may be reconstructed with the separated image data received, whereby the reduction of data amount and reproduction of the original image of high quality are realized. Further, use of the separated image data provides a high speed image data transmission.
The image structures of the first piece and the second piece of image data and the selection data are determined when the image data is generated. The characteristics of those data and the resolution of the input device also determine the image structures. This necessitates correct combining of the separated image data irrespective of their image structures. The same thing is true also for a case where the image data, while being separated, are stored in the image data base, for example, and the image data is referred to. The fact that a quality output image or picture cannot be secured unless the image structures of the input image data are conformed to the image structure of the output device, is also true.
The present invention handles the first piece and the second piece of image data and the selection data to selectively specify the first piece or the second piece of image data, which make up input image data, in the following manner: those separated data are received; the image structures of the separated data are conformed into the image structure of an output device; then those image data are combined; and the combined image data is output.
Thus, the invention reproduces an original image or picture of high quality irrespective of the image structures of the input image data since the separated image data are combined after the image structures of the separated data are conformed to the that of the output device.